Millions of tractor-trailer rigs are operated on the roads everyday. These large vehicles are a primary source of logistics for all types of goods and products and are capable of handling large loads. The average fuel economy for a tractor-trailer vehicle is about six miles per gallon. Fuel costs is one of the most significant categories in operating a tractor-trailer vehicle. Many attempts have been made to optimize fuel consumption in order to reduce the overhead costs of operating a tractor-trailer vehicle. One area of development for improving fuel economy is the utilization of what is known in the art as down sped motors. The concept behind down sped motors is to maintain engine RPM's low so as to reduce the fuel injection cycles and as such improve the fuel economy of the vehicle. Lower engine RPM's results in lower fuel consumption and as such can reduce the cost of operating a tractor-trailer vehicle.
One issue with the aforementioned is the increased strain on the drivetrain components. Existing implementations of a down sped motor include rear end differential gear of ratios such as but not limited to 1.91-2.40 to 1. These low gear ratios result in a lower engine RPM at cruising speed of the vehicle but also result in less torque transferred to the drive wheel. One major issue with utilizing the aforementioned gear ratio to achieve a lower engine RPM is the torque remains in the drivetrain components and as such results in broken u-joints and other component failure. Having conventional transmission ratios and rear end gears can result in an increase fuel consumption under certain conditions. When a driver encounters more adverse conditions such as steep roads or high winds, the driver will apply more accelerator to maintain vehicle speed which results in lower fuel economy.
Accordingly, there is a need for a vehicle drivetrain system that is configured to maintain a lower engine RPM while further providing reduced torque on the drivetrain components and wherein the drivetrain system allows engine RPM's to be lower at cruising speed so as to improve fuel economy.